3.7.3.1 The Processor and it's Components. Flashcards
What do processors contain?
ALU.
Control Unit.
Numerous Registers.
Define an ALU.
Performs arithmetic and logic operation.
E.g. addition or XOR.
Define Control Unit.
Controls the various components of the processor.
Controlling the fetch-execute cycle.
Define a Register.
Small storage locations use to hold data temporarily.
Define a Program Counter (register).
Used to hold the memory address of the next
instruction to be executed in the fetch-execute cycle.
Define a Current Instruction (register).
Holds the instruction that is currently being executed
by the processor.
Define a memory address register.
) Stores the memory address of a memory location
that is to be read from or written to.
Define a status register.
Contains a number of bits, the values of which can
change to indicate the occurrence of an interrupt.
Outline the role of the clock.
The system clock generates a timing signal which changes at a regular frequency. This signal is used to synchronise the communication between the components of the processer and the rest of the computer system.
Outline the components of the cpu
Processor
System bus
I/O controllers
Main memory
Processor purpose
To control different types of devices
Processor components
Control unit
ALU
registers
Control unit purpose
Managing all computer operations through the fde cycle
Fetch
Instruction is fetched from main memory
Decode
Instruction is broken into opcode and ooerand - may also send signals into the ALU
Execute
Execute the instruction
Registers definition
Special memory cells which operate at very high speed - used by arithmetic and logic operations.
3 parts of the system bus
Address bus
Control bus
Data bus
System bus definition
Connects all components in the computer using wires on the motherboard
Data bus definition
Bi directional bus used to transport data and instructions between the three components of the three bus model.
Is the data bus single or bi directional
Bi directional
How many wires does a data bus usually have
32
Effect of a larger data bus
Larger the data bus the more data that can be transported at one time
Width of the data bus
Is a key factor in determining the overall system performance
Adress bus definition
Bus that carries signals from cpu to main memory and I/O devices
Adress bus single or bi directional
Single
Memory is divided into
Units called words.
Typical size of a word
8,16,32
Or 64 bits in size
What happens when a cpu requests data from main memory
Send the address of the word to main memory via the address bus, then main memory returns the data along the data bus.
Example in assembly code: LDA 23
this code would be sent from the cpu along the address bus.
Data at memory location 23 would fhen be sent back to the cpu via the data bus
Width of address bus
Address bus of 3 bits (3 wires) then you would only have 8 different addressable blocks of memory.
(2^8)
How to calculate memory.
2^n
Control bus - bi or single directional
Bi directional
Number of wires in control bus
More than 16
Control bus definition
Used to transport control signals and instructions between thre components of the three box model. Such as when a device has finished a job or has just been plugged in
Main memory definition
Store program instructions and data - the only data store that can be directly accessed from the cpu
Simplest part of the computer in the priciple of the main memory
IAS (immediate access store)
Main memory is made up of
RAM chips but can include one of more ROM chips
Von nuemann machine
Data and instructions are saved in main memory.
Instructions sent to the processor via the system bus.
I/O is performed by IO devices.
Data travels from the I/O devices to the processor and main memory via the system bus.
Stored program definition.
Program must be resident in main memory to be executed,
Machine code instructions are fetched from main memory one at a time, decoded and executed in the processor.
Harvard architecture machine defintion
Has a seperate store for data and instructions.
Throughput is faster since there are faster since there are seperate stores for data and instructsionsnans seperate buses to connect them to the processor.
Memory consists of
Data stored in addresses.
The more main memory
The more addresses youll have
RAM defintion
Used for readable and writable memory. Used by the processor to store (write) and load (read) data.
ROM purpose
To find and load the first lines of code for the operating system.
Modern CPU’s have
Internal memory (cache) and I/O devices have the ability to access memory without the need for the CPU, the address bus has go be bi-directional. However, the exam will treat it as uni-directal.
Some modern systems combine
Combine address and data buses since they are used at different parts of the fde cycle.
ROM nowadays is
Hard to write flash memory
Flash memory requires
Special equipment, voltages od processes.
Flash memory read only or write and read
Isnt true read only as you can change it with some difficulty e.g. if you havent updated your bios.
